Applying Gauss weapon technologies to essentially an Auto-Shotgun, I've come up with this. It should handle like an auto-shotgun, and give performance sort of like a light grenade launcher. This model is a little expensive with an integrated gyro-stabilizer, holographic sight. The thought is that each ammunition type would calibrate the power used to accommodate the differing payload weights providing consistent performance. I wanted to keep the muzzle velocity sub-sonic to keep the weapon silent, but it would be dialed up for certain ammo types, the APDS comes to mind. Standard load would be something like a shotgun flechette load. I'm thinking a bullpup design, with a magnetically fed magazine that might allow a mix of ammo types without having to change mags.

2cm Gauss Multi-Role Launch System
A large-caliber man portable Gauss weapons system. Using the proper ammunition and accessories, the G-MRLS can fill the roles of lower tech rifles, shotguns, light grenade launcher, and squad support weapons, with a single flexible weapons system. Although not designed for high-precision, long-range engagements, with the proper ammunition, this weapon can be used successfully in many engagement scenarios. The integrated gyro-stabilizer, holographic sight, and 300mps muzzle velocity ensures that any user will be able to drop their payload with precision. This weapon is designed specifically to use the ammunition types on the table below. The standard ammunition is a 20 sub-caliber flechette load.

Kinetic kill AP would require high speed, hence ridiculous recoil from a 20 mm gun (cannon?).
HEAP would be a better fit for the concept?

Otherwise I agree that the concept should be very possible.

I think you are assigning a little to much damage over the board. A standard gauss rifle dart is 4D AP5 and that is neither silent nor low-recoil. A current rifle round at 2 - 3 kJ muzzle energy is 3D damage, a current anti-materiel rifle with a muzzle energy of perhaps 18 kJ is rated at 5D damage. 18 kJ in at a subsonic speed would require a round of 18000 = m × 250²/2, m ≈ 0.6 kg = 600 g.
3 kJ (so 3D damage) would require a ~100 g projectile.

Kinetic kill AP would require high speed, hence ridiculous recoil from a 20 mm gun (cannon?).
HEAP would be a better fit for the concept?

Otherwise I agree that the concept should be very possible.

I think you are assigning a little to much damage over the board. A standard gauss rifle dart is 4D AP5 and that is neither silent nor low-recoil. A current rifle round at 2 - 3 kJ muzzle energy is 3D damage, a current anti-materiel rifle with a muzzle energy of perhaps 18 kJ is rated at 5D damage. 18 kJ in at a subsonic speed would require a round of 18000 = m × 250²/2, m ≈ 0.6 kg = 600 g.
3 kJ (so 3D damage) would require a ~100 g projectile.

At the same muzzle energy it would have a heavier projectile at lower speed than a shotgun, so more powerful recoil. Bulky, or even Very Bulky trait is called for, especially for auto fire.

A random-order access magazine would be bulky for such substantial rounds (something like 20 × 50 mm?)?

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Thanks AnotherDilbert! I appreciate your input, these are a bunch of really great points.

The formatting suggestion is ugly, but it does solve the problem.

1. The weapon has built-in gyro stabilization. Maybe it would have the Very Bulky trait without it, and you could deal with this with an expensive grav compensator, IC harness, Battle Dress, or a big Aslan.

2. You're right, sub-sonic is stupid. This is a 2cm cannon, not a shotgun. Have to keep my eye on the mission.

3. A low MV might be useful if you wanted to use it in an indirect fire capacity. Combined with guided rounds, this would let you drop HE/HEAP/guided rounds on targets behind cover

4. Once the MV is back up to 1000m/s AP/APDS rounds become more viable. Both types would need to be sub-calibre, but honestly, a 10mm penetrator is still pretty frightening.

5. I'm liking a bullpup design to provide a longer barrel, more magnet time. Rear-mounted ammunition, and power pack, would offset the weight of the heavier magnets in the front part of the barrel.

6. Gauss weapons would generally have less recoil for a given projectile mass, because you don't have the extra mass from propellant, substantial at higher calibers.

7. The higher muzzle velocity should support the higher damage. With regular ammunition it would be less effective vs hard targets (no AP) than an anti-material rifle but still very damaging. I am assuming 5 TL of engineering.

8. I don't understand some of the alternate ammo statistics/traits. Solid shot adds additional AP, but I would assume that the default ammo for a weapon would be engineered to be at least as effective as solid shot. It would seem like most of the alternate ammo types would replace any AP trait from the weapon, and replace with any new traits. i.e. why would incendiary gauss rifle ammo still be AP 5? Plasma Gauss pistol rounds?

A civilian version could use these stats, and drop the auto trait. A purely military version could have the Auto trait and gravitic compensation, and more power in a heavier package designed for BattleDress usage. This would provide a more versatile weapon for TL13+ troops other than having to try and solve every problem with plasma/fusion weapons. Sometimes you just don't want to cause quite that much damage.

For Gauss weapons especially, I like bullpup configurations because it maximizes barrel length, which has would reduce the energy requirement for any given ring of magnets and keep heat as low as possible. There isn't really enough, unclassified, information on usable coilguns to be able to speak more knowledgeably about what makes a good Gauss weapon, but this sounds right absent hard data.

I appreciate the input. I'll reconfigure and resubmit for further feedback. Numerous Gauss weapon issues are being addressed under this post. viewtopic.php?f=89&t=120714

AnotherDilbert has excellent points, I would, of course, be pleased to see anyone else's thoughts.

Against near peer opponents, likely targets would be armoured infantry within line of sight.

Sounds like a job for HEAP man! Although, there doesn't seem to be any mechanics for improvement of these sorts of basic technologies as TL increases. a TL5 HEAP round should be superceded by a TL12 HEAP round.

I forgot a TDX based HE round. anyone have thoughts on a shaped TDX charge warhead?

Most modern militaries do not take shotguns seriously as combat weapons anymore; they're armchair warrior and hollywood weapons. Shotguns have the issue of being short-ranged so not very flexible as a primary weapon for a soldier. If they're not the primary weapon, then they're a secondary weapon, and no soldier wants to lug around another whole weapon. Most shotguns you see in the hands of soldiers today are used for opening up doors and so on - not as combat weapons and they've become increasingly smaller as they're no longer weapons but tools.

When considering rounds, you might want to consider the public relations cost of them. I'm serious, the PR value. A short-ranged weapon shoots clouds of flechettes really only has one use: butchering civilians (who lack armor), particularly protestors (who will be packed in groups to make launching a flechette swarm worthwhile and lack weapons so will be close). If you're fighting enemies with anything approaching proper weapons, they're going to be out of the range of a "future shotgun", they may have armor that will make a "shotgun" round ineffective, and they're not going to clump up in a way that makes indiscriminate swarms of flechettes worthwhile.

That doesn't mean that a low-velocity gauss launcher system is useless - I just don't think that "shotgun" is one of the better uses for it if is a military weapon. I think it'd be more useful as a low signature (low noise, doesn't produce muzzle flash, and so on) method to deploy short-ranged packages. A grenade launcher / light mortar for local indirect fire, an anti-armor system to engage light vehicles and battle dress as a weapon of last resort, a way to shoot signal flares, lay mine-clear explosive line, shooting cord/line/rope over short distances, a flare launcher, and a smoke launcher I think would a device like this' forte.

Most modern militaries do not take shotguns seriously as combat weapons anymore; they're armchair warrior and hollywood weapons. Shotguns have the issue of being short-ranged so not very flexible as a primary weapon for a soldier. If they're not the primary weapon, then they're a secondary weapon, and no soldier wants to lug around another whole weapon. Most shotguns you see in the hands of soldiers today are used for opening up doors and so on - not as combat weapons and they've become increasingly smaller as they're no longer weapons but tools.

When considering rounds, you might want to consider the public relations cost of them. I'm serious, the PR value. A short-ranged weapon shoots clouds of flechettes really only has one use: butchering civilians (who lack armor), particularly protestors (who will be packed in groups to make launching a flechette swarm worthwhile and lack weapons so will be close). If you're fighting enemies with anything approaching proper weapons, they're going to be out of the range of a "future shotgun", they may have armor that will make a "shotgun" round ineffective, and they're not going to clump up in a way that makes indiscriminate swarms of flechettes worthwhile.

That doesn't mean that a low-velocity gauss launcher system is useless - I just don't think that "shotgun" is one of the better uses for it if is a military weapon. I think it'd be more useful as a low signature (low noise, doesn't produce muzzle flash, and so on) method to deploy short-ranged packages. A grenade launcher / light mortar for local indirect fire, an anti-armor system to engage light vehicles and battle dress as a weapon of last resort, a way to shoot signal flares, lay mine-clear explosive line, shooting cord/line/rope over short distances, a flare launcher, and a smoke launcher I think would a device like this' forte.

Thanks Epicenter! Great points.

We've moved away from the "shotgun" role, and more into a flexible Gauss Weapons System. It isn't going to be as rapid fire as a lower TL Autocannon, nor deliver as large a payload as a Grenade Launcher, or RAM GL, but should be able to perform as a great, hard-hitting projectile weapon with indirect file capability. I'm seeing it as more of a Squad support weapon for non-battle dress equipped troops, among other roles. Imperials working at TL15 will be using heavier weapons with Artillery Battle Dress, but lower tech troops, Mercs, or shipboard Marines conducting boarding/anti-boarding exercises might find it useful.

Most modern militaries do not take shotguns seriously as combat weapons anymore

No, they take them quite seriously. The are a special weapon used in a number of circumstances. Mostly centered around Close Quarters Combat. i.e. Boarding actions, close urban combat and entries is where you will see them, they more common in these days of Asymmetric warfare. Effectively they are a support weapon.

Basically, most infantry engagements in the modern era take place from twenty five to fifty metres, to two to three hundred metres, hence the assault rifle weapon system was developed to optimize results at these ranges.

Then you have close up and personal, where a submachine gun or a carbine is more handy.

If you watch recent films like John Wick and Atomic Blonde, you realize at that range, almost anything can become lethal. if you have the training, reflexes and karma points.

Close quarters relies also on stealth and non detection, otherwise people with infra goggles and motion detectors would start blasting holes in the wall with the shotgun.

Close range in corridors doesn't allow much evasion, so a shotgun spread tends to hit.

No, they take them quite seriously. The are a special weapon used in a number of circumstances. Mostly centered around Close Quarters Combat. i.e. Boarding actions, close urban combat and entries is where you will see them, they more common in these days of Asymmetric warfare. Effectively they are a support weapon.

I have yet to see any first line military that takes a shotgun seriously as a combat weapon anymore; most militaries have them in their TO&E but you simply don't see very many of them anymore. When you do see them, they're specialized tools for breaching and "lockpicking" and less for shooting at people. The primary weapon remains a modern "carbine" size weapon; even submachine guns are dying out in military use to modern "carbine" weapons. (This isn't getting into recent thing of militaries considering returning to a more "battle rifle" size cartridge for a general issue weapon.)

No, they take them quite seriously. The are a special weapon used in a number of circumstances. Mostly centered around Close Quarters Combat. i.e. Boarding actions, close urban combat and entries is where you will see them, they more common in these days of Asymmetric warfare. Effectively they are a support weapon.

I have yet to see any first line military that takes a shotgun seriously as a combat weapon anymore; most militaries have them in their TO&E but you simply don't see very many of them anymore. When you do see them, they're specialized tools for breaching and "lockpicking" and less for shooting at people. The primary weapon remains a modern "carbine" size weapon; even submachine guns are dying out in military use to modern "carbine" weapons. (This isn't getting into recent thing of militaries considering returning to a more "battle rifle" size cartridge for a general issue weapon.)

I can say from first hand experience that the Navy (Well, the Australian Navy at least) take them very seriously as weapons for a boarding party. Clearing and crew control are jobs shotguns are perfect for in the tight confines of a ship. I can't say I'd like to have one in an open field, but their use is certainly still there.

Even our standard rifles, the Austeyr, were almost never taken aboard for boardings (Though the bowman in our RHIB kept one handy) and they're probably one of the more compact designs you're likely to find in a modern rifle.

So I think, "Quite useful for certain things" is a fair category to stick them into.

I can say from first hand experience that the Navy (Well, the Australian Navy at least) take them very seriously as weapons for a boarding party. Clearing and crew control are jobs shotguns are perfect for in the tight confines of a ship. I can't say I'd like to have one in an open field, but their use is certainly still there.

Even our standard rifles, the Austeyr, were almost never taken aboard for boardings (Though the bowman in our RHIB kept one handy) and they're probably one of the more compact designs you're likely to find in a modern rifle.

So I think, "Quite useful for certain things" is a fair category to stick them into.

That matches my experiences as well with the USN, note in my brief period onboard a Carrier it wasn't uncommon to see the ship's Marines to be using when on security alerts and the like. Shotguns are common with entry teams as well.

Wargaming it, you could have assault squads armed with shotguns, much like you had assault sections armed with submachine guns. This is effective when faced with unarmoured troops, at likely close quarters.

If you upgun a shotgun, you come out with a grenade launcher, useful when facing armoured Space Marines.